Identification and Characterization of a Novel Human Aldose Reductase-like Gene

Abstract

We have identified a novel human protein that is highly homologous to aldose reductase (AR). This protein, which we called ARL-1, consists of 316 amino acids, the same size as AR, and its amino acid sequence is 71% identical to that of AR. It is more closely related to the AR-like proteins such as mouse vas deferens protein, fibroblast growth factor-regulated protein, and Chinese hamster ovary reductase, with 81, 82, and 83%, respectively, of its amino acid sequence identical to the amino acid sequence of these proteins. The cDNA of ARL-1 was expressed in Escherichia coli to obtain recombinant protein for characterization of its enzymatic activities. For comparison, the cDNA of human AR was also expressed in E. coli and analyzed in parallel. These two enzymes differ in their pH optima and salt requirement, but they act on a similar spectrum of substrates. Similar to AR, ARL-1 can efficiently reduce aliphatic and aromatic aldehydes, and it is less active on hexoses. While AR mRNA is found in most tissues studied, ARL-1 is primarily expressed in the small intestines and in the colon, with a low level of its mRNA in the liver. The ability of ARL-1 to reduce various aldehydes and the locations of expression of this gene suggest that it may be responsible for detoxification of reactive aldehydes in the digested food before the nutrients are passed on to other organs. Interestingly, ARL-1 and AR are overexpressed in some liver cancers, but it is not clear if they contribute to the pathogenesis of this disease. Aldose reductase (AR)1 is a NADPH-dependent enzyme that was first identified by its ability to reduce glucose to sorbitol (1). There are strong indications that it is involved in diabetic complications (2). However, its physiological function is not entirely clear. It is quite abundant in the epithelial cells lining the collecting tubules in the renal medullar. Since hyperosmotic stress can induce the transcription of AR, followed by the accumulation of sorbitol to a level that can affect intracellular osmotic pressure, it was proposed that AR may be involved in the osmoregulation in the kidney (3). In the seminal vesicles, AR may be involved in the production of fructose that is abundant in the semen because sorbitol can be converted to fructose by sorbitol dehydrogenase (1).Besides kidney and testes, AR is present in many other tissues where its function is not clear. Interestingly, glucose is not its preferred substrate (K m ϭ 100 mM, k cat /K m ϭ 2.8 ϫ 10 2 M Ϫ1 min Ϫ1 ) (5). It is more efficient in reducing various aromatic and aliphatic aldehydes including glyceraldehyde, benzaldehyde, pyridine aldehyde etc. (6). In particular, AR's ability to reduce methylglyoxal (K m ϭ 7.8 M, k cat /K m ϭ 1.8 ϫ 10 7 M Ϫ1 min Ϫ1 ) (7), a toxic byproduct of glucose metabolism, and 4-hydroxynonenal (K m ϭ 22 M, k cat /K m ϭ 4.6 ϫ 10 6 M Ϫ1 min Ϫ1 ) (8), a toxic lipid aldehyde produced during oxidative stress, suggests that it may be responsible for detoxifying these and other harmful aldehydes generated by cellular metaboli...

Detection and identification of tumor-associated protein variants in human hepatocellular carcinomas

“…In addition, we used 5 other histologically examined human HCC samples together with the corresponding normal liver tissue from the Institute of Molecular Biology, University of Hong Kong. These tissue samples (group II) were designated identically to those published by Cao et al 24 : (T, tumor; N, normal tissue) T2;N2, T12;N12, T16;N16, T19; N19, and T23. HBV/HCV status was determined in these HCC samples by polymerase chain reaction for HBV DNA and HCV RNA.…”

“…After 2-DE separation of the soluble protein fraction of HCC tissue (400 g protein/sample), 2-DE gel areas (Ϸ30 -40 kd/pI Ϸ6.2-7.8) containing the hARLP region were excised from 2-DE gels and blotted onto hydrophobic polyvinylidene difluoride membranes (0.2 m Bio-Rad, Hercules, CA) under semidry conditions for 3 hours at 1 mA/cm 2 membrane at room temperature with 50mM borate buffer, pH 9.0, 20% methanol. For immunodetection of hARLP the polyclonal antibody directed against the last 17 amino acids of the C-terminus of the hARLP, accession number (acc) O60218, 24 was used (dilution 1:1,000) according to the method described earlier. 35 The hARLP antibody was produced for our laboratory by Bio-Genes (Berlin, Germany).…”

“…5 In human HCC, an aldose reductase-like-1 (ARL-1) mRNA was expressed. 24,25 Two aflatoxin B1-inducible aldehyde reductases were discovered in aflatoxin-B1-induced rat hepatomas 26 and in human colonic carcinomas. 27 These results led us to perform a proteome analysis of human HCC.…”

Inhibitory effects of polyphenols isolated from Rhus verniciflua on Aldo-keto reductase family 1 B10

“…Aldo-keto reductase family 1 B10 (AKR1B10), also identified as aldose reductase-like or small intestine aldose reductase (ARL-1), is a recently identified member of the aldo-keto reductase (AKRs) superfamily (1). AKR1B10 is a NADPH-dependent oxidoreductase and reduces various aldehydes and ketones, including endogenous substrates such as retinals, farnesal and geranylgeranial (2,3).…”

Detection of polyol accumulation in a new ovarian carcinoma cell line, CABA I: a1H NMR study

“…Regarding tumours, an aldose reductase activity has been Experimental Therapeutics identified in rat hepatoma, in which it was suggested to play an important role in cell detoxification from harmful metabolites, such as aldehydes, generated by intracellular metabolism. Moreover, this enzyme has been reported to display a high sequence homology with a novel human aldose reductase, overexpressed in human liver cancer (Cao et al, 1998). Recent studies also reported that aldose reductase can convert daunorubicin into its reduced form, daunorubicinol, thus decreasing the pharmacological activity of this anti-tumour drug (Ax et al, 2000).…”